Chris Hill write:
On 24/09/15 18:41, Phil Endecott wrote:
Chris Hill wrote:
Suitably processed this could provide a source of building outlines.
Yes, I think it could be very useful for that. I've had a play
and rather than doing shaded relief I've just converted the height
directly into a grey shade. I've then applied ImageMagick's edge
detection filter. Here are a couple of fragments near Manchester
taken from the 25cm resolution data; in each case the first image
is the direct height-to-grey and the second is edge-detected:
http://chezphil.org/tmp/lidar1.png
http://chezphil.org/tmp/lidar1_ed.png
This is at SJ 8099, or maybe search for Chaseley Road to find it
on a map. You could easily trace building outlines from this and
determine roof shapes and could measure building heights by subtracting
roof from ground, with some suitable tool. You could also trace
trees and some walls.
http://chezphil.org/tmp/lidar2.png
http://chezphil.org/tmp/lidar2_ed.png
This is SE of the last one at SJ 8198. The gasometers (presumably!)
are at the junction of West Egerton Street and Liverpool Street.
I find it interesting that you can count the number of ridges in
the large warehouse roofs. You can also easily identify carparks!
How would people find this for tracing compared to photo imagery?
Looks interesting. Have you reprojected the images from the OS
projection they come as to WGS84 that OSM uses?
No, I've just processed the raw values in their OSGB form.
I don't really have the skills to do reprojection and tiling and
serving the tiles as a map layer; if people actually want to use
this, someone else will need to do that.
Some of the data was gathered in 2009, so Bing aerial images can be more
up-to-date, but for most buildings this isn't a problem.
The data does at least indicate its age.
Regards, Phil.
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